Best Directions

Energy gains and losses through windows are a strong function of a particular window’s U-factor and solar heat gain coefficient (SHGC), of course, but orientation plays a critical role as well. Far too often, for my taste, I’ve observed that the facade with the greatest number of windows on a production built home tends to face the backyard, whatever its orientation. To get a feel for just how much of an effect a window’s orientation can have, I modeled the energy impacts of placing three different types of windows in four separate locations on both a summer and a winter day. All six of the bar charts shown in Figures 1–6 depict solar gains and conductive losses in Btu/ft2 for a single 24-hour day with clear skies at 40º north latitude (approximately the latitude of Denver, Reno, and Salt Lake City). Figures 1–3 depict conditions for January 21, with an average temperature of 20ºF. Figures 4–6 depict conditions for July 21, with an average temperature of 85ºF.Net gains help in the winter and hurt in the summer. &...